Process and apparatus for zero indexing op
a number wheel on a calculator



Dec. 12, 196? E. STAUTMEISTER 3,

PROCESS AND APPARATUS FOR ZERO INDBXING OF A NUMBEH WHEEL ON ACALCULATOR Filed Aug. 10, 1966 INVEN TOR ERICH STAUTMEISTER Aitorney gUnited States Patent M PROCESS AND APPARATIZTS FOR ZERO INDEXING 0F ANUMBER WHEEL ON A CALCULATOR Erich Stautmeister, Gottmadingen, Germany,assignor to Avo Apparatebau Vogt A.G., Kreuzlingen, Switzerland FiledAug. 10, 1966, Ser. No. 571,491 Claims priority, application Germany,Aug. 13, 1965, A 49,995; Jan. 20, 1966, A 51,375 6 Claims. (Cl. 235144)ABSTRACT OF THE DISCLOSURE A zero resetting arrangement for numberwheels wherein the resetting cam is gradually actuated by a zero indexlever. The lever is not directly actuated by the resetting solenoid, buta motion transmitting means is interposed between the solenoid and indexlever. The latter means comprise a ratchet mechanism, actuated by thesolenoid and a yieldable spring means between the ratchet and indexlever whereby the lever is given a gradual motion towards the cam.Movement of the reset solenoid is controlled by an interrupter whichoperation is controlled by a cam on the ratchet wheel.

The present invention relates to the apparatus for zero indexing orresetting of a number wheel of a calculator, especially anelectromagnetic calculator, whereby each number wheel is mechanicallyconnected with a heartshaped curved reset cam member which serves as theinner cam for actuation by a zero indexing lever.

In the prior art, the reset cams are actuated to zero position by levermeans actuated directly by solenoids. Due to inertia forces and initialhigh current flow to the solenoids, the lever means forcefully andsuddenly contact the cams and cause undue wear on the cam surfaces. Suchsudden actuation also causes the number wheel to which the cams areconnected to override or overrun their Zero position. Examples of suchdirect actuation of the cam levers by the solenoid means are shown inUS. Patent No. 2,980,329 to Hoifman and in US. Patent No. 3,050,250 toMann.

One object of this invention is to gradually reduce the impact contactbetween the cams and their zero index levers and thereby reduce the wearbetween these elements.

Another object is to reduce the forces with which the zero index leversactuate the resetting cams by controlling and varying the forces exertedby the solenoid means upon the index levers.

Another object is to introduce a ratchet and spring device between thesolenoid means and the zero index lever means and to also introduce aswitch control for the solenoid means whereby the zero indexing forcesare reduced and the resetting cam motion takes place gradually withoutundue wear and without overrunning of their zero position.

Other and further objects of the invention will become apparent from aconsideration of the drawings and the more detailed description whichfollows and which form a part of the present specification.

In the drawing, the new device of the present invention is shown in twodifferent operational positions, as follows:

FIG. 1 shows the present device for zero indexing of the number wheel inthe inoperative position and without any connection for movement withthe number wheel;

FIG. 2 shows the device of FIG. 1 in the operating position at a stageduring the stopping of the number wheel after its return to zero; and

3,357,537 Patented Dec. 12, 1967 FIG. 3 shows a schematic view of theself-interrupting electromagnetic switch device.

The number wheel 1 in the figures of the drawing is fitted with aheart-shaped curved cam member 2 and both are mounted rotatably on asingle axis which is in the center of the wheel 1. At the bottom of thewheel 1 in FIG. 1 the zero index lever 4 which is biased by the spring 5and which is rotatable around the zero index lever axis 12 in adirection which brings the head of the lever towards the heart-shapedmember when elongating and tensioning the spring 5. The ratchet wheel 6has two driver pins 7 as well as two cams 8 on its periphery and ismounted rotatably on the ratchet wheel shaft 9. On the zero index lever4 and at a lower edge thereof there is provided a stop 10 which projectsfrom the body of the lever and serves as a safety stop for the circularratchet wheel spring 11 which is wrapped around the axis 12.

The pawl 14 moves the wheel 6 in clockwise direction step by step whilethe retaining spring 13 acts only as a detent to preventcounterclockwise rotation of the wheel. The counterclockwise rotationcould occur under the influence of the springs 5 and 11 when stop 7contacts 11, especially when the wheel 6 has a position between thedesigned positions in FIG. 1 and FIG. 2.

As stated above, the retaining spring 13 engages the outer periphery ofthe ratchet wheel and the spring tine fits into the ratchet to preventit from being turned backwards. The advance of the ratchet wheel isaccomplished by the driving pawl 14 pushing the wheel forward orclockwise, the anchor lever 18 being directly connected to the drivingpawl 14 and being tiltable forwards and backwards about the anchor pivot19. The anchor lever 18 is moved to the left by the electromagneticsolenoid 17, the tension of the spring 16 increasing thereby.Consequently pawl 14 will drop behind the next tooth. Through theself-interrupter, shown in FIG. 3 and described subsequently, theelectromagnetic solenoid 17 is interrupted and the spring 16 can movethe anchor lever 18 with the pawl 14 to the right. The wheel 6 turns fora section of a tooth in direction of the arrow. This sequence is beingrepeated to provide a stepwise movement until one of the cams 8 cuts offthe switching contact 15 of the self-interrupter. The movement of thezero index lever 4 between the position shown in FIG. 1 and the positionshown in FIG. 2 is accomplished through the transient connection of thedriver pin 7 to the spring 11. The zero index lever 4 is moved by thespring 11 in the direction of the arrow because the projecting driverpin engages the upper surface of spring 11 during the clockwise movementof the ratchet wheel and the lever 4 tilts in the counterclockwisedirection about its axis 12 and as shown by the arrow applied to lever 4in FIG. 2. This movement of the lever engages cam member 2 and moves itin the direction which brings about the zero position of the numberwheel. It is possible to vary the forces acting to move index lever 4 inaccordance with the energy supply by varying the number of teeth of theratchet wheel, through one or several driver pins 7, as well as throughthe adaptation of the number of switching cams 8. In the figures, twodriver pins 7 and two switching cams 8 are shown but more may be used.The ratchet wheel 6 continues to run after completion of the zeroindexing process, until the electromagnet 17 is cut off via theswitching contact 15 which is shown schematically in FIGS. 1 and 2.

The number wheels 1 move slowly from a dead stop because of the inertiaof their mass and because of the initial resting condition. A rigidconnection of the electromagnet with the zero index would not help inachieving an accurate zero setting from a dead stop. When the numberwheel is in position to permit the zero index lever to touch theheart-shaped curve member in the vicinity of the axis, the energyimpinging upon the heart-shaped curve member rises quadratically withthe distance of the anchor lever from the electromagnet. The strikingenergy is least whenever the zero index lever engages the point of theheart-shaped curve member most remote from the axis 3 of the numberwheel and the energy is highest when it engages the heart-shaped curvemember at a point close to the axis 3, e.g. at the short cusp.

Thus, an important feature of the present invention is that the strikingenergy is at a minimal value of the energy range when the zero indexlever engages the heart-shaped curve member at a point remote from theaxis, based upon the electromagnetic interrupter mean which permitsslower zero indexing with greater accuracy. The new function of thisimproved electrical interrupter means shown in FIG. 3 will become moreapparent from the more detailed description which follows.

The self-interrupter, shown in FIG. 3, comprises the electric conductor21 which is intermittently connected to the locally fixed contactelement 2.2 by means of the contact element 23. The contact element 23projects from the interrupter member 25 which is pivotally movable aboutits axis 24. The movement of interrupter member 25 is limited betweenmagnet 26 and fixed contact element 22. The permanent magnet 26 servesas a stop and as a limitation of the angle of horizontal swing of theinterrupter member 25. FIG. 3 also shows the connection f conductor 21to the electromagnet 27 and of the latter to the negative terminal ofthe battery.

The anchor lever 29 of the interrupter is swivelable about the axis 28located at the bottom of the anchor lever. The pawl 30 is pivotallyconnected to anchor lever 29 and includes a U-shaped end 31 whichencloses the free end of the interrupter member 25 at the U-shaped end31.

The mode of operation of the self-interrupter, shown in its closed stateis as follows: when a current flows in the conductor 21 the anchor lever29 is attracted by the electromagnet 2 7, which imparts a swingingmovement to the interrupter 25 via the rearward movement of the pawl3t), e. g., to the left, as shown in FIG. 3, and up to the stop on thepermanent magnet 26. Simultaneously, however, the contact 22, 23 isinterrupted, and the magnetic effect of the electromagnet 27 on theanchor lever 29 is eliminated. The anchor lever 29 is then again pulledtoward the right, in FIG. 3, under the influence of the spring 32 whichurges the interrupter member 25 into closed position with contact 23.Since the interrupter 25 consists of magnetic metal for example, a steelsheet, this interrupter remains attracted to the permanent magnet 26until the end 31 of the pawl brings it again into the contact position.Depending on the width of the opening of the U-shaped part, a larger orsmaller predetermined delay is provided.

If the interrupter 2.5 were prevented from adhering to the permanentmagnet 26 or if there were no play in the connection between the pawl 33and the interrupter 25, then the interrupter 25 would movesimultaneously with the anchor lever 29, a rapid flickering would occurin the interrupter contact, e.g the contacts 23, 22 would open and closein rapid sequence. This flickering is an undesirable disadvantage. Amore sluggish reconnection of the opened contact is preferred. Thedesired predetermined delay which is achieved depends on the width ofthe U-shaped opening of the end 31 of the pawl and makes the process ofzero indexing more accurate while eliminating wear.

The operation is as follows: When the number wheel must be returned tozero the switch is first closed by hand. The interrupter is in theclosed position shown in FIG. 3 and the device is in the position ofFIG. 1. Current flows through the electromagnetic solenoids 17 and 27(which may be the same). The anchor lever 18 and the anchor spring 16are so built that the lever 18 is in its left position before theinterrupter opens the contacts 22 and 23. When contacts 22 and 23 areopen no current flows in the electromagnetic solenoids 17 and 27. Thepawl 14 moved by spring '16 switches the wheel 6, and the contacts 22and 23 will reclose by spring 32 so that current can again fiow throughthe electromagnetic solenoids 17 and 27. This sequence is repeated untilone Of the cams 8 cuts oif the switching contact 15 and thereby currentto solenoids 17 and g7.

As can be seen from FIGS, 1 and 2, the zero index lever 4 ends in thedriver spring 11. This spring 11 is the point of application formovement by the driver pin 7 under the clockwise movement of the ratchetwheel 6. This driver spring 11 is a leaf spring with inherentflexibility in-the leaf end which cancels out the rigid connection andadapts itself admirably to the requirements of energy absorption duringthe zero indexing process. The leaf spring makes the impact of hittingthe heart sha-ped curve member less dependent on the relative positionof the heart-shaped curve member and the electromagnet 17 storessuflicient energy for the zero indexing steps. The balance of the energyfrom the electromagnet is against the energy of the spring 16 whichreturns the anchor lever 18 toward the right to move pawl 14 to rotatewheel 6.

From the foregoing, it is seen that the switching step of the ratchetwheel 6 is accomplished tensionally by the spring 16 together with theenergizing movement of the electromagnet. This 'spring tension andelectromagnetic energizing movement permits the impact of th zeroindexing lever upon the heart-shaped curve member to be come independentof the distance of the anchor lever. When using two driver pins 7 andonly one switching camj8, it will be possible to carry out two zeroindexing processes, one after the other. Both indexing processes runtheir course before switching off of the electromagnet via the switchingcam 8, as shown by the lifting of the upper contact of switch 15 by cam8 in PEG. 1.

. slaim 1.- Apparatus o ero in exi the nu b r Wheel f an el c omagneticc sulatg comp isin a rth p 3 11 membe oper t ely c nnec ed t e um Wheel,a p o ed zer inde lev r ha n one e f g ng a d moving d am member and itsass c a Wheel to zero position, a spring device carried by the other endof aid in e lever, a ratche Whee engag ng means ri d y th ratchet hee oC II BCI a d p i device and there y more the i d x lev a sol no d m an apawl means to actuate step-by-step said ratchet wheel, means onn ct ng asolenoid n p wl m ans, an ne u'p er c nt o ing the e s zation of s id lnoid means n epeated in ervals o impart a radual movement to saidengaging means and thereby gradually and yielda ly mo e the sp ingdevice a d index l ver tow and ga ns th am mem er for a zero res ing opeation.

2- The pparatus e fo th in cla m 1, whe th 1 e ting means comprises anarm tur le er drawn by th olenoid t move he paw me ns n s e k and springmeans biasing the armature lever towards the working stroke- 3. Theapparatus set forth in claim 1, wherein the interrupter comprises twocontacts, one of which is of magnetic material, interrupter solenoidmeanscontrolled by the contacts, lost-motion means connecting saidinterup e olenoid means and h m gnet c ta to m ve it alternately to openand closed positions, and a permanent magnet to act as a stop for saidcontact in its opening direction,

4 The apparatus set forth in claim 1, wherein a plurality of spacedengaging means are carried by the ratchet wheel to permit a series ofzero indexing operations.

5. The apparatus set forth in claim 1, wherein means 5 for terminatingthe operation of said interrupter means means is operatively connectedWith the ratchet Wheel to terminate the interrupter operation at apredetermined point of the wheels movement.

6. The apparatus set forth in claim 3, further comprising a cam carriedby the ratchet Wheel and a switch means in series With the interruptermeans, said cam means opening said switch means to terminate theoperation of the interrupter means.

References Cited UNITED STATES PATENTS Loosii 235144 Hoffman 235144 Mann235-444 Hartkorn 235144

1. APPARATUS FOR ZERO INDEXING THE NUMBER WHEEL OF AN ELECTROMAGNETICCALCULATOR COMPRISING: A HEART-SHAPED CAM MEMBER OPERATIVELY CONNECTEDTO THE NUMBER WHEEL, A PIVOTED ZERO INDEX LEVER HAVING ONE END FORENGAGING AND MOVING SAID CAM MEMBER AND ITS ASSOCIATED WHEEL TO ZEROPOSITION, A SPRING DEVICE CARRIED BY THE OTHER END OF SAID INDEX LEVER,A RATCHET WHEEL, ENGAGING MEANS CARRIED BY THE RATCHET WHEEL TO CONTACTSAID SPRING DEVICE AND THEREBY MOVE THE INDEX LEVER, A SOLENOID MEANS, APAWL MEANS TO ACTUATE STEP-BY-STEP SAID RATCHET WHEEL,